"He raised the wand to shoulder height, said "Waddiwasi!" and pointed it at Peeves. With the force of a bullet, the wad of chewing gum shot out of the keyhole and straight down Peeves's left nostril; he whirled right way up and zoomed away, cursing."

Etymology

Latin vade, "travel." Possibly Swedish vadd, meaning "soft mass" (in this case, gum); or French vas y, "go there," as Lupin also directed the object upwards; or possibly from the English wad, as in "a wad of gum". Waddiwasi may also be a combination of the words wad and kamikaze. In this case, the spell's function is most likely to be as simple as causing a wad of something to launch itself sacrificially at someone nearby. As the perfect spitball launcher, such a charm would doubtless have been a favorite tool in the arsenal of troublemakers like Moony, Wormtail, Padfoot and Prongs.